Commonly used materials, such as artificial building materials, furniture, plastic products, adhesives, clothing and the like, generate formaldehyde gas which adversely affects graphic material.
Generally speaking, a coupler in emulsion type silver halide color photographic material customarily comprises a support and a plurality of silver halide emulsion layers each having sensitivity to respectively a different spectral range and containing a coupler for forming a dye when the coupler reacts with a product oxidized with a color developing agent on said support. For example, silver halide emulsion layers normally which are sensitive to blue, green and red light and contain yellow, magenta and cyan couplers in respective layers.
After image exposure, each of the silver halide emulsion layers is then color-developed to form a yellow, magenta and cyan dye image thereon, respectively.
In such a multi-layered color photographic material, an excellent color-image can be obtained only when sensitivity and contrast are well-balanced between the above-mentioned silver halide emulsion layer. It is therefore desired that the photographic characteristics of such a multi-layered color photographic material does not change even after long preservation including the periods before and after exposure up to the time of development. If a coupler in an emulsion type silver halide color photographic material is in an atmosphere containing formaldehyde before it is colordeveloped, the coupler reacts with formaldehyde and is consumed and produces an undesirable reaction product. Consequently, this results in serious deterioration of photographic characteristics, such as lowering color density or gamma, a color stain, and increased fog.
To prevent photographic characteristics from deteriorating by reaction with formaldehyde, which is referred to herein as a toxic gas, it has been proposed to use a compound which makes formaldehyde non-toxic by reacting therewith (hereinafter referred to as an aldehyde scavenger). U.S. Pat. No. 2,309,492 discloses that a very small amount of formaldehyde produces a yellowish product through the action to a pyrazolone coloring agent and causes color-fog in a photographic element, and proposed to use an aldehyde scavenger such as hydroxylamine, a hydrazine derivative, a hydrazo derivative, semicarbazide, dimethylhydroresorcine or naphthylenediamine.
U.S. Pat. No. 2,895,827 discloses the problem that formaldehyde is produced from the support of a printing paper coated with an aldehyde resin such as urea-formaldehyde or malamineformaldehyde, and proposes an urea- or melamine-sizing layer on the surface of the support to serve as an aldehyde-scavenger.
U.S. Pat. No. 3,652,278 discloses a variety of compounds containing an amine or amide such as N,N'-ethylene urea, acetamide, N,N'-diacetyl ethylenediamine, monomethylamine, or dimethylamine, to serve as a scavenger for formaldehyde gas in the air.
Japanese Patent Examined Publication No. 34675/1971 proposes N,N-ethylene urea, 2,3-dihydroxynaphthalene, dimedone, and the like, for the similar purpose.
U.S. Pat. No. 3,811,891 and Japanese Patent Examined Publication No. 23908/1976, for example, also propose many types of scavengers for aldehyde.
From studies made by the present inventors, although there are some differences of the capability for scavenging aldehyde among most of the above-mentioned scavengers, all of the scavengers displayed almost similar scavenging capability. It is therefore obvious that the above-mentioned scavengers should be added in large quantity so that the photographic characteristics under discussion will be at a satisfactory level. However, as is well-known in the art, it is not possible to add a great quantity of an aldehyde scavenger because such aldehyde scavengers have the disadvantage that the physical properties of the photographic emulsion layer are deteriorated. For example, coating firmness becomes substantially weaker and the photographic characteristics thereof are also affected. However, when the amount of the aldehyde scavenger is such so as to not seriously deteriorate the physical properties of the photographic material and to not lower the photosensitivity and other photographic characteristics, the amount is insufficient to prevent deterioration of the photographic characteristics by formaldehyde.
In the meantime, with respect to the relation between the above-mentioned toxic gas and couplers, it has been confirmed that photographic characteristics are lowered by a toxic gas regardless of the kind of coupler which is used. In particular, the influence of such toxic gas in serious when using the so-called "Four-equivalent coupler" in which a substituted group is introduced on the active site of the molecules and is apt to be relatively more serious in the case of a yellow and magenta coupler than in the case of a cyan coupler, and inter alia, the magneta couplers are most seriously affected.
The present inventors have studied how formaldehyde gas reacts with the 5-pyrazolone-four-equivalent coupler that is the most polular magenta coupler, and have been unable to find any coupler capable of greatly preventing deterioration of photographic characteristics. It has also been known that the bad influence of toxic gases such as formaldehyde gas are diminished by increasing the relative amount of a hydrophobic and high boiling point organic solvent to that of the lipophilic coupler. Although this is an improvement, the results are still unsatisfactory. This sometimes causes undesired changes such as a physical property change of the coated layer when the relative amount of the high boiling point organic solvent is increased. The permissible relative increase in the amount of said solvent is therefore limited.
There have recently been reported various types of magenta couplers, which are less reactive with a toxic gas such as formaldehyde gas. Such magenta couplers have strong resistance against such gases. For example, in U.S. Pat. No. 3,214,437, 3,253,924, 3,311,476, 3,419,391, 3,617,291, 3,926,631, 3,522,052 and 3,227,554; Japanese Patent O.P.I. Publication No. 126833/1981; etc., disclose two-equivalent couplers as examples of such couplers.
When using such two-equivalent couplers, there are many cases in which, for example, (i) color-fog is seriously caused, (ii) reaction activity is not proper or (iii) the couplers are chemically unstable, so that the couplers become a substance incapable of developing color with the passage of time, and there is further such an inconvenient facet as the difficulty in synthesizing the couplers. The actual situation is therefore that no satisfactory coupler is known.
It is an object of the invention to provide a silver halide color photographic material whose photographic characteristics do not deteriorate with resultant lowering of color density or gamma, occurrence of a color stain or increase in fog, even when the photographic material is exposed to a toxic gas such as formaldehyde gas for a long time until it is finally color-developed.
Another object of the invention is to provide a silver halide color photographic material in which the formaldehyde substance is improved and deterioration of the physical properties of the coated layers and the photographic characteristics do not occur.